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Abstract:
Mesoscale eddies modulate the stratification, mixing and dissipation pathways, and tracer transport of oceanic flows over a wide range of spatiotemporal scales. The parameterization of buoyancy and energy fluxes associated with mesoscale eddies thus presents an evolving challenge for ocean modelers, particularly as modern, state-of-the-art climate models approach eddy-permitting resolutions. Here we present a parameterization targeting such resolutions through the use of a sub-grid mesoscale eddy kinetic energy budget framework. Our study presents two novel insights: (1) both the buoyancy and momentum effects of eddies can be parameterized using a kinetic energy backscatter; (2) the dominant factor in ensuring a physically-accurate backscatter is the vertical structure of the parameterized fluxes. We present idealized simulations of a 1/2 and 1/4 degree resolution model with backscatter applied to the equivalent barotropic mode. Remarkably, the global kinetic and potential energies, isopycnal structure, and vertical energy partitioning are consistent with a 1/32 degree reference solution. This work provides guidance on how to parameterize mesoscale eddy effects in the challenging eddy-permitting regime.
